1. Technical Field
This invention relates to slider-suspension assemblies for data recording information storage systems and to a method for making such assemblies. In particular, the invention relates to an improved slider-suspension assembly for a magnetic storage system and a method for electrically connecting the slider to the suspension.
2. Description of the Related Art
Information storage devices, which include magnetic storage devices and optical data storage systems, utilize at least one rotatable disk with concentric data tracks containing the information, a transducer for reading data from or writing data to the various tracks, and a head positioning actuator connected to a head for moving it to the desired track and maintaining it over the track centerline during read or write operations. The transducer is attached to a head (or "slider") having an air bearing surface which is supported adjacent the data surface of the disk by a cushion of air generated by the rotating disk. The slider is attached on its back side (the side opposite the air bearing surface) to the suspension, and the suspension is attached to an actuator arm of the head positioning actuator.
The suspension provides dimensional stability between the slider and actuator arm, controlled flexibility in pitch and roll motion of the slider relative to its direction of motion on the rotating disk, and resistance to yaw (radial) motion. The suspension typically provides a load or force against the slider which is compensated by the force of the air bearing between the slider's air bearing surface and the disk surface. Thus, the slider is maintained in extremely close proximity to, but out of contact with, the data surface of the disk. The suspension typically comprises a load beam, which is mounted at one end to the actuator arm, and a flexure element which is attached to the other end of the load beam and supports the slider. The load beam provides the resilient spring action which biases the slider toward the surface of the disk, while the flexure provides flexibility for the slider as the slider rides on the cushion of air between the air bearing surface and the rotating disk. Such a suspension is described in U.S. Pat. No. 4,167,765, which is assigned to the same assignee as this application. An example of a conventional slider is described in U.S. Pat. No. 3,823,416, which is assigned to the same assignee as this application.
In the conventional slider-suspension assemblies, the slider is mechanically attached to the flexure of the suspension by epoxy bonding. The electrical connection between the transducer and the disk drive read/write electronics is made by twisted wires which run the length of the suspension load beam and extend over the flexure and slider. The ends of the wires are ultrasonically bonded to the transducer leads on the slider. The fabrication of such a slider-suspension requires manual assembly and is thus time consuming and costly.
Another type of suspension is a composite or laminated structure comprising a base layer, a patterned conductive layer with patterned electrical leads formed thereon, and an insulating layer in between, as described in IBM Technical Disclosure Bulletin, Vol. 22, No. 4 (September, 1979), pp. 1602-1603. In this laminated suspension, the slider is epoxy bonded to the laminated suspension and the transducer leads are soldered to the electrical leads formed on the suspension.
Another laminated structure type of suspension is comprised of a base layer of stainless-steel, an insulating layer of polyimide formed on the base layer, and a patterned conductive layer of etched copper alloy formed on the insulating layer, as described in U.S. Pat. No. 4,996,623. The etched copper layer provides a lead structure electrically connecting the thin-film magnetic head transducer and the disk drive's read/write electronics. A method for attaching a slider to a laminated/etched suspension in a data recording disk file has been described in U.S. Pat. No. 4,761,699 and IBM Technical Disclosure Bulletin, Vol. 36, No. 2, February, 1993, p. 371.
There are several disadvantages associated with the slider-suspension assembly process described in U.S. Pat. No. 4,761,699. In order to carry out the process, the etched flat cable on the suspension must undergo further processing to have an insulating passivation layer formed on the cable to prevent shorting between the slider and the cable. Vias must be opened through the passivation layer in order to make electrical contacts with the slider, and solder bumps must be reflowed both for mechanical as well as electrical termination. The slider must also undergo vacuum processing to provide solderable metallized contact pads on the back side of the slider for mechanical attachment. Moreover, the head-suspension assembly must be heated in an infrared belt furnace for reflow of the solder bumps which subjects the slider and MR head to high temperatures. Such a reflow also requires some kind of flux which might induce corrosion on the MR head. An additional step is required to clean off the flux subsequent to the reflow. Additionally, this process is batch type and is not Continuous Flow Manufacturing (CFM) or automated assembly line compatible.
The process described in IBM Technical Disclosure Bulletin, Vol. 36, No. 2, February, 1993, p. 371, uses epoxy for mechanical attachment of the slider. The ends of the copper alloy leads of the suspension are bent up from the surface of the suspension and soldered to the head termination pads using the batch type reflow process. This process brings in a tooling complexity to hold the leads against the solder pads on the slider during the reflow process. In addition, this process has the disadvantages associated with a batch type reflow process as described above.
It would be desirable to provide a method for the fabrication of a data recording disk drive slider-suspension assembly that allows for some tolerance in the alignment of the slider to the suspension when it is mechanically attached, while providing a simple and effective method of electrical connection between the thin-film magnetic head transducer and the suspension leads. It would further be desirable to provide a method of soldering the transducer termination pads to the lead pads of an etched copper cable by a process without the use of flux and the need for subsequent cleaning. It would be still further desirable to provide a method of soldering the transducer termination pads to the lead pads of an etched copper cable by a process such that the head and the suspension are not subjected to heat exposure, thus preventing high temperature exposure and magnetic degradation to temperature sensitive components like an MR head. It would be still further desirable to provide a process for suspension lead and head termination pad connection that does not require a furnace reflow process, thus making the process CFM compatible.